Porcelain tooth and backing for dental bridgework.



. I I W'. LSTEWART. I

PORCELAIN TOOTH AND BACKING FOR DENTAL BRIDGEWOBK APPLIOATIOI; FILED DEC. 23, 1912. Y H

' Patented Dec. 30, 1913.

WILLIA J. STEWART, or NEW YORK, n. Y.

PORCELAIN TOOTH AND BACKING FOR DENTAL BRIDG-EWORK.

To all 'wlwm'z't may concern Be it known that'I, WILLIAM J. STEWART, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Porcelain Teeth and Baokings for Dental Bridgework,

of which the following is a specification.

My invention relates to certain new and useful improvements in porcelain teeth and backings for dental bridge work, the primaryobject of the invention being to provide a construction of tooth; and backing whereby the usual cracking and splitting strains towhich teeth of this character are customarily subjected will be transmitted in the form of, crushing strains, which the tooth is better able to withstand, thus reducing to the minimum liability of breakage of the applied tooth.

A further object of the invent-ion is to provide a construction which insures the firm locking engagement of the tooth with its ,backing, but which at the same time permits of the ready removal of a tooth from the backing to enable errors or defects to be I corrected 'or an old tooth to be conveniently replaced with a new one in the event of accidental breakage.

'A still further object of the invention is to provide a construction whereby the backmg may be firmly secured to the bridge and the tooth to the backing, and whereby a strong, rigid and durable fastening of the tooth imposition is insured. Y

The invention consists of the featuresof construction, combination and. arrangement of- .partshereinafter fully described and claimed, reference being had to the accompanying dra wings, in which Figure 1 is a rear perspective view of'one form of porcelain tooth embodying my in vention. Fig. 2-is a front perspective view of a backing used in connection therewith. Fig. 3 isa vertical longitudinal section throughthe connected tooth and backing 1n the plane of one of the dove-tailed grooves and locking lugs. Fig. 4 is a horizontaltransverse section through the connected toothand; backing. Fig. '5 is a sectional Specification of Letters Patent.

Application filed December 23, 1912. Serial the same.

Patented Dec. 30, 1913. No. 738.254.

view similar to Fig. 3 of the toot-h disconnected from the backing. Figs. 6 and 7 are horizontal transverse sections through the tooth on the lines 6 6 and 77 of F ig.'5. Figs: 8 and 9 are similar sections through the backing on corresponding planes. Fig. 10 is a rear perspective view of one member of a two-part backing which may be employed. Fig. 11 is a front perspective view of the other member of the two-part backing. Fig. 12 is a view corresponding to Fig. 3 of a tooth connected with the form of backing shown in Figs. 10 and 11. Fig.

13 is a horizontal transverse sectionthrough' Fig. 14 is a rear elevation of a modified form of tooth. Fig. 15 is a vertical longitudinal'section of the same. Fig. 16 is a rear elevation of a form of backing used in connection with the tooth shown in Figs. 14 and 15. Fig; 17 is a. front elevation of the backing. Fig. 18 is a central vertical longitudinal section of the same.

Fig. 19 is a similar view through the connected tooth and backing. Fig. 20 is a vertical section through a tooth and'backing as designed especially for use in central laterals, cuspids, bicuspids and molars. Fig. 21 is a similar view'through the backing per se.

Referring to Figs. 1 to 9, inclusive, of the drawings, 1 designates a porcelain tooth front, and 2 its backing. As shown, the back of the tooth front 1 is plane-surfaced and intersects the butt end of the tooth,

which is beveled downwardly and rearwardly to .provide an inclined abutment shoulder 3. The said rear face of the tooth front is provided with a pair of longitudinal grooves 4 each opening at one end through the shoulder 3 andintersecting and communicating at its opposite end with a recess 5. Between the grooves the body of the tooth is left intactto form a longitudinal rib 6. Each groove 4 and the recess 5 communicating therewith, as well as the rib 6, is tapered, wedge-shaped. and of, dove-tailed formation. As illustrated, the front and side walls of the groove preferably extend on elliptical arcs and incline or s'lope'downwardly and inwardly,while the I rear walls of the recess also slope down- .may be cemented wardly and inwardly and the sides of the rib 6 incline or slope downwardly and outwardly. By this construction, the surfaces of the receiving grooves and recesses provide aseries of beveled or inclined planes for a purpose hereinafter fully explained.

The backing 2 comprises a plate substantially coextensive in area with that of the back and butt of the tooth front 1, said plate being bent at one end obliquely to provide an abutment surface 7 for the surface 3 of the tooth front. The inner face of-this backing carries a pair of longitudinally extending lugs 8 having projecting lower ends 9 'and spaced to form an intervening groovelO, said' lugs being adapted to fit within the grooves 4 and recesses 5 and said groove 10 being adapted to receive the rib 6. The lugs are wedge-shaped or tapered and provided with sloping orinclined surfaces corresponding to those of the grooves 4, recesses 5 and rib 6, whereby the tooth is adapted to he slipped endwise in one direction into locking engagement with the backing and to be held firmly against removal except by a reverse endwise motion.

It will of course, be understood that the direction of locking action is in the direction of the pressures falling upon the tooth during mastication, and that in the locking e11- gagement the beveled walls bind firmly against each other and frictionally hold the tooth in position upon the backing.

When the tooth is. placed permanently upon the backing for. use upon a bridge, it against any possibility of casual displacement in the direction of its releasing motion, while the construction described permits of its ready removal and replacement in case of accidental breakage and of both the tooth and backing being ground or trimmed to any extent without liability of injury on account of the firm support obtained.

It will be observed that the locking bev el'ed surfaces of the tooth and its backing afi'ords both anterior and posterior support in such a way as-to transmit or make all pressures coming from mastication a crushing pressure on the porcelain thus' giving the tooth the fortification of the resistance of porcelain to; crushing pressure as opposed to the weaker strength or power of resistance of the porcelain to cracking or splitting pressures, whereby liability o injury to the tooth from the strains received .in ordinary'service is reduced to the minimum.

In the modified form of my invention shown 'in Figs. 10- to 13',-inclusive, the construction of the tooth is the same as that previously described, but a two-part back: ing is employed. This backing comprises ,ing lugs tooth above the forms of construction an inner plate 11 having an oblique abutment end or flange 12 toengage' the sur face 3 of the tooth and provided with longitudinal slots or openings 13 to receive lock- 14 similar in construction to the locking lugs 8 but which. are carried by a plate 15 adapted to bear against the outer surface of the plate 11, through the openings 13 in which the lugs-1 L project to engage the receiving grooves and recesses in the tooth. This construction admits of the use of different materials in the construction of the backing to suit special purposes or to secure economy of manufacture.

In the form of my invention shown in Figs. 14 to 19, inclusive, grooves 16 and recesses 17 corresponding in form to the grooves 4 and recesses 5, shown in'Figs. 1 to 13, inclusive, are formed in the tooth, but the intervening rib 18 terminates below the plane of the abutment surface 3, which is cut away onan the arc of curvature of the face of the tooth, making the groove 16 of somewhat greater depth. In conjunction with this form of tooth I provide a backing plate 19 provided with looking lugs 20 and groove 21 of the shape and construction before described, but connected at their inner 'ends by a cross piece 22 which is of proper form to close the opening at the top of the rooves 16. This form of construction of the tooth and backingmay be used throughout the entire number of 'facings employed in dental bridge work, including central laterals, cuspids, bicuspids and molars, or wherever full porcelain chewing surfaces are not absolutely'essential.

In the adaptation of the invention to a molar facing, or other tooth facing where a full porcelain chewing surface is desired, the body and crown of the tooth may be of solid formation, as illustrated by the form of tooth 23 shown in Fig. 20, in which the back of the tooth-extends on a curved line contour and is provided with looking portions of the character before described In conjunction with this tooth, a curved plate backing 24 is employed having locking lugs of the stated character. rib upon the tooth may be cut away to allow the grooves to intersect at the ends opposite the recesses 5, .and in a somewhat similar manner to that shown in Fig. '14, to provide a clearance space 25 for greater convenience in applying and removing the tooth to and from the backing.

It will be observed thatin the different which may be employed, the tooth is locked to the backing and bridge in an absolutely firm and secure manner against any possibility of movement in any direction under pressure from mastication, while at the same are concentric .with that of As indicated, thean intermediate disclosed, others of e correspondingly lugs and termlnal projections to interlock through the action of the several surfaces is in the form of a crushing pressure, which porcelain is better able to resist, than asplitting pressure, such as porcelain teeth of ordinary construction are subjected to, and under which they are liable to split or break. By my construction the tooth is not only better adapted to Withstand the'imposed strains, but is firmly backed against all transmitted pressures, whereby its strength and durability is considerably increased.

Another material advantage arising from my construction is that a defective tooth may be readily removed and replaced upon a fixed bridge without injury to the bridge or backing, and ground down with the backing to any desired extent without injury to either. Furthermore, the parts of the backing may be made by stamping or milling and supplied at a comparatively low cost. Where 'a backing of the intended kind is not at hand, the dentist may also readily and conveniently form a backing from thin metal by annealing the backing into the grooves to secure firm locking action. It will, moreover, be observed that the construction is such that a firm and durable support for the tooth may be secured without exposure of the backing from the front.

I claim 1. A porcelain tooth having wedge-shaped grooves formed in center and between its center and side edges,

said grooves having walls converging in one direction and intersecting undercut wedge-shaped sockets at one end thereof, the front walls of said grooves extending on curved lines corresponding to the lon tudinal and transverse curvature of t e labial surface, and a backing provided with arranged wedge-shaped with said grooves and sockets.

3. A porcelain tooth having longitudinal wedge-shaped dovetailed grooves in its inner face on opposite sidesof its longitudinal center, with a wedge-shaped rib between the grooves, said, grooves opening at one 'end through said abutment surface and communicating at their opposite ends with wedge-shaped recesses, the opposed walls, of

said'grooves and ribextendlng on convergtooth, said sets 1ts rear face on opposite sides of its longitudinal center and between and a backing ing lines toward the recesses,

to engage the having an ofl'set abutment abutment surface 'of the tooth and spaced lugs with projections corresponding in form to and adapted to engage and interlock with said grooves and recesses.

4. A porcelain tooth provided in the back thereof with longitudinal wedge-shaped, dovetailed grooves arranged on opposite sides of its center and between its center and side edges, said grooves having entrance ends opening throu h the butt end of the tooth and having t eir opposite ends terminating in recesses whose Walls slope downwardly and forwardly and also downwardly and inwardly toward the center of the tooth, said grooves extending divergently from their entrance ends to said re- .cessesand each groove having its walls converging from itsentrance end to said socket and sloping toward the center and front of the tooth, and a backing having correspondingly arranged and shaped lugsto engage said grooves and recesses.

5. A porcelain tooth and backing rovided with sets of interengaging connectlons on opposite sides of the medial longitudinal line thereof and arranged to interlock wholly on the interior of the body of the of connections, respectively, having abutting surfaces sloping converently toward the lingual and morsal surfaces of the tooth.

6. A porcelain tooth and backing provided with interlocking, intersliding, dovetailed, wedge-shaped grooves and lugs on opposite sides of the longitudinal centers thereof, said grooves and lugsextending in diverging relation from the shoulder of the tooth toward the morsal surface of the tooth and interlocking wholly within the plane of the body ofthe tooth, the respective grooves and lugs having the surfaces thereof sloping convergently toward the lingual and morsal surfaces of the tooth.

7. A porcelain tooth provided in its rear face with longitudinal, dovetailed, wedgeshaped grooves arranged between the center and side edges of the tooth and extending in divergent relation from the shoulder portion toward the morsal or biting surface of the tooth, the respective walls of said grooves terminating at their inner ends in abutment surfaces which extend into the tooth on a; plane sloping toward the labial and morsal surfaces of the tooth, and a backing provided with correspondingly shaped and arranged lugs to interlock with said grooves.

8. A porcelain tooth having grooves wholly within the plane of the tooth and on opposite sides of its longitudinal center,

said grooves terminating in abutment surfaces which extend into the tooth on a plane 5 nally disposed loc sloping froin the lingual surface forward vature of the labial surface, substantially as and downward toward the labial and 11101"- described.

sal surfaces. In testimon whereof I affix my signature 9. An'artificial tooth having a longitudiin presence 0 two witnesses.

king groove on the lingual WILLIAM J. STEWART.

side extending from the shoulder toward the Witnesses: L norsal surface on eurved lines correspond: CHAS. HIBSON, ing to the longitudlnal and transverse cur- ELEANOR L. MURRAY. 

